Friction clutch

ABSTRACT

The present small diameter low cost clutch units embody improvements over those of our U.S. Pat. Nos. 1,985,301 and 2,214,789 centered in the release levers, which, while still affording the mechanical advantages of the previously patented clutches of higher engaging pressure with lighter pedal pressure for disengagement, are pivotally connected at their outer ends to the drive lugs on the pressure plate and have novel low friction oscillatable stirrup type fulcrum members to fulcrum the levers near their outer ends on the spider or back plate. These stirrup members compensate by their oscillation for the slight change in center distance between the fulcrum and pivot pin during clutch operation for not only lower friction but reduced wear, while the pivot pin tieup of the levers with the drive lugs on the pressure plate results in the levers giving added engaging pressure due to centrifugal force, which advantage can easily be augmented by adding weight to the back of the levers at their outer ends. The stirrups may be of one piece I-shaped construction, as in one of the present clutches, or of an adjustable type, as in the other clutch.

United States Patent Thelander [451 Apr. 4, 1972 [54] FRICTION CLUTCH W.Vincent Thelander, P.O. Box 385, Sugar Loaf Mountain Ranch, Cave Creek,Ariz. 85331 22 Filed: June 1,1970

21 Appl.No.: 42,013

[72] Inventor:

[52] US. Cl. ..192/99 A, 192/98, 192/7029, 285/8, 267/174 [51] Int. Cl...Fl6d 21/00 [58] Field of Search ..192/99 A, 70.26, 70.29, 70.3, 192/89R, 98 A, 105 C; 285/83; 267/174, 177, 178

[56] References Cited UNITED STATES PATENTS 502,620 8/1893 Fisher..85/8.3 2,021,973 11/1935 Wenp.... ....l92/99 Primary Examiner-Mark M.Newman Assistant Examiner-Randall Heald Attorney-Andrew F. Wintercorn[57] ABSTRACT The present small diameter low cost clutch units embodyimprovements over those of our US. Pat. Nos. 1,985,301 and 2,214,789centered in the release levers, which, while still affording themechanical advantages of the previously patented clutches of higherengaging pressure with lighter pedal pressure for disengagement, arepivotally connected at their outer ends to the drive lugs on thepressure plate and have novel low friction oscillatable stirrup typefulcrum members to fulcrum the levers near their outer ends on thespider or back plate. These stirrup members compensate by theiroscillation for the slight change in center distance between the fulcrumand pivot pin during clutch operation for not only lower friction butreduced wear, while the pivot pin tieup of the levers with the drivelugs on the pressure plate results in the levers giving added engagingpressure due to centrifugal force, which advantage can easily beaugmented by adding weight to the back of the levers at their outerends. The stirrups may be of one piece l-shaped construction, as in oneof the present clutches, or of an adjustable type, as in the otherclutch.

11 Claims, 13 Drawing Figures Patented April 4, 1972 3 Sheets-Sheet 1 mN M M E 5 Wm M a w V W if g A T TOR/V5 Patented April 4, 1972 5Sheets-Sheet 2 ATTORNEY Patented April 4, 1972 I5 Sheets-Sheet 5 398.5LB.X3 n75 TOTAL TRAVEL I R a M a W D mwBGAG S NEN O R IL E 4TER T J I RA T A A PR 4.A =TN F 2R3SO 0 KW 4 5 W L R E T N E. C 2 B Y M a L4 4SHAFT l6 FIG 10' m R W 4 w a W m w a N W W ATTORNEY FRICTION CLUTCH Thisinvention relates to friction clutches for use on automobiles and othervehicles, the new mini cars, for example, having created the need for asmaller diameter, low cost, clutch unit, and the present invention beingmore particularly concerned with improvements in the type of clutchdisclosed in Thelander et al. US. Pat. No. 1,985,301 and my U.S. Pat.No. 2,214,789, in which, by virtue of the use of novel springpressedrelease levers, the back plate can be reduced to an open spider form,exposing the pressure plate for cooler operation and longer clutch platefacing life.

In the clutches disclosed in the patents referred to, the leversoperated by the throw-out collar to engage and disengage the clutch arepivotally mounted so that the engaging springs have a certain mechanicaladvantage to obtain multiplied engaging pressure, while there isnevertheless a mechanical advantage derived in the disengaging operationof said levers by the throw-out collar so that the clutch can bedisengaged with lighter pedal pressure. A clutch of that general designpresents special problems in its practical applications for which it isthe principal object of my present invention to provide solutions byimprovements in design and construction.

One object with the present design is to provide a clutch of the typementioned having a low friction stirrup type fulcrum between the spiderand each of the spring-pressed release levers near the outer endthereof, which is pivotally connected to the pressure plate, the novelstirrup serving also by its freedom to oscillate to compensate for anyslight change in center distance between its V-shaped fulcrum and thepivot pin in the pressure plate during clutch operation, the ability tocompensate for the variation in center distance between the two pivotsresulting in a further considerable reduction in friction and wear thatwould otherwise have to be tolerated, while the pivot pin tieup of thelevers and spring system with the sturdy pressure plate assuressufi'icient strength to withstand the highest centrifugal effect, whilethe present design loses none of the important advantages of theaforementioned patented constructions, namely:

1. Exposure of the pressure plate for good heat dissipation, a coolerpressure plate giving longer facing life on the clutch plate;

2. The multiplied lever ratio inherent in the patented designsnecessitating only three springs instead of the usual six or nine, andthe fact that the springs are located between the levers and the spiderand are therefore out of contact with the pressure plate, which is theheat dissipating member, so that the springs are not subjected to hightemperatures and there is no spring pressure loss due to loss of temper;

3. The spider, being of stamped sheet metal construction and largely ofchannel section, provides rigid support for the lever fulcrums so thatthere is very little deflection and consequently very little loss ofpedal travel due to deflection, and

4. It is still possible to insert shipping spacers between the outerends of the levers and the spider, which are removed after the clutchhas been mounted on the flywheel.

Another object with the present design is to impart a small amount ofadditional engaging pressure to the pressure plate due to .thecentrifugal effect of locating the levers center of gravity above thefulcrum, the amount of this effect being variable easily by slightdesign changes, as for example, forming a lip on the release lever inproximity to the pivot pin and welding a weight thereto at apredetermined radius with respect to the pivot axis.

Another object is to provide for ease of assembly of the stirrups byinsertion through slots in the lever and spider, and also having thepivot pins, which are easily assembled on the levers through holes inthe drive lugs on the pressure plate, each provided with a groove in themiddle portion through which a compressible resilient roll pin can beeasily inserted in the lugs to lock the pivot pins in place withoutriveting or using cotter pins or lock rings.

Another object is to provide a clutch of the novel design describedabove in which either of two means can be used for easily setting all ofthe release levers at uniform engaging height:

1. An adjusting screw can be provided at the inner end of each leverhaving a rounded surface on the adjusting head end arranged to makepoint contact with the throwout bearing, or

2. Special stirrup bolts of T-design can be used, each having one pairof fulcrums on the crossbar of the T to rock on the spider and anotherpair of fulcrums provided on a collar slidable on the threaded shank andarranged to rock on the lever while being adjustable longitudinallyrelative to the bolt by means of an adjusting nut threaded on the rearend of the shank.

The invention is illustrated in the accompanying drawings, in which:

FIG. 1 is a rear view of a clutch embodying my invention;

FIG. 2 is a cross-section on the line 2-2 of FIG. 1, indicating indotted lines a portion of the flywheel and driven shaft along with thethrowout bearing, that is, of course, operable in the usual way by meansof the clutch pedal (not shown);

FIGS. 3 and 4 are views corresponding to portions of FIGS. 1 and v 2 butshowing an adjustable stirrup for each release lever in lieu of theadjusting screws at the inner ends of the levers;

FIGS. 5 and 6 are two views at right angles to one another of one of thestirrups used in the clutch of FIGS. 1 and 2, showing this part on alarger scale;

FIG. 7 and 8 are two views at right angles to one another of one of thelever pivot pins, shown on a larger scale;

FIG. 9 and 10 are views at right angles to one another of one of thecompressible resilient roll pins used for locking the pivot pins inplace without riveting or using cotter pins or lock rings, while stillfacilitating assembly and reducing cost;

FIG. 11 and 12 are views at right angles to one another of one of therelease levers, FIG. 11 being a section on the line 11-11 of FIG. 12 andincluding a showing in dotted lines of an additional feature of arearwardly projecting lug on the back of the pivoted end of the leverhaving a small weight welded thereto to add a desired amount ofadditional pressure on the pressure plate due to centrifugal effect,this effect being variable, of course, by merely varying the amount ofweight added, and

FIG. 13 is a geometrical diagram to enable a better understanding of thepresent stirrup fulcrum friction clutch construction, the centrifugaleffect that accounts for additional pressure on the pressure plate byvirtue of this novel construction being omitted from consideration inthis diagram.

Similar reference numerals are applied to corresponding parts throughoutthe views.

Referring first to FIGS. 1, 2, and 5 to 12, the reference numeral 14designates a flywheel mounted on the rear end of a crank shaft 15 andforming the driving element. A shaft 16 constituting the driven elementextends rearwardly from the clutch into the gear box of the transmissionin the usual way. At 17 is indicated the clutch throwout bearing movablein the usual way by means of the clutch pedal (not shown). The clutchcomprises a disk 18 carried on a hub 19 splined on the front end of theshaft 16, and a pressure plate 20 disposed behind and in concentricrelation with the matted portion of the disk 18 to cause engagementthereof with the flat face 22 on the flywheel. In accordance with thedisclosure in Thelander et al. US. Pat. No. 1,985,301, a plurality ofrelease levers 23 are provided which are arranged to be depressedagainst the action of compression springs 24 by clutch pedal operationof the throwout bearing 17 against the inner ends 25 of the levers todisengage the clutch. In the Thelander et al. US. Pat. No. 1,985,301, aswell as in my US. Pat. No. 2,241,780, these levers 23 were pivoted onthe spider 26 near the outer end to transmit pressure of the springs 24in a multiplied degree to the pressure plate 20, and, while the pressureof the springs 24 is multiplied through the levers 23 for clutchengagement, it is nevertheless clear that there is an appreciablemechanical advantage also in the disengagement of the clutch by reasonof the fact that the springs 24 are closer to the pivots than the innerends 25 of the levers 23 where the throwout bearing 17 engages, and thismechanical advantage accordingly makes for lighter pedal action. Thereis still another advantage in this location of the springs 24 withrespect to the pivots from the standpoint that there is very little lossof spring pressure when the clutch facings or mats 21 become worn,because there is so little expansion of the springs permitted inproportion to a given amount of wear of the facings.

In accordance with the present invention, however, I have pivotallyconnected the outer ends of the release levers 23 by pivot pins 27 tothe drive lugs 28 that extend rearwardly from the pressure plate 20.These have flat side faces parallel to one another and to radii of thepressure plate slidably engaging the opposite sides of slots 29 providedin the vertical back wall 30 of the spider 26 so as to transmit drivethrough the spider 26 and pressure plate 20 to the clutch disk 18.Furthermore, in accordance with the present invention, each of therelease levers 23 is fulcrumed near its outer end on an I-shaped stirrupmember 31, the cross-portions 32 and 33 at opposite ends of whichprovide pairs of fulcrum surfaces 34 and 35 coined on the inner edges,as best appears in FIGS. and 6, for line contact antifriciton fulcrumingof the cross-portion 32 on opposite sides of the slot 36 in therearwardly embossed portion 37 of the spider 26, and similar fulcrumengagement of the other cross-portion 33 on opposite sides of the slot38 of the forwardly embossed portion 39 of the web of the generallychannel-shaped release lever 23 next to the pivoted outer end thereof.The slots 36 and 38 are long enough and wide enough in relation to thecross-portions 32 and 33 of the stirrup member 31 to permit insertionthrough these slots in assembling the stirrup members 31 on the spiderand levers after the spring-24 for each lever has been assembled inplace resting on the circular seat 40 defined for one end of the springon the spider 26 while the other end has line bearing contact atdiametrically opposite sides of the other end on a crossbar 41 definedin the semi-open end of the frusto-conical pocket 42 provided on therelease lever 23 intermediate the ends thereof, a lug 43 being struckinwardly from the end of the pocket 42 on one side thereof to engage inthe end of the spring 24 and assure its remaining always in centeredrelationship to the crossbar 41.

The pivot pin 27, for each release lever 23, is received in a hole 44 inthe drive lug 28 and registering holes 45 in longitudinally extendingflanges 46 provided on the release lever, and has an annular groove 47provided at the middle thereof, as best shown in FIG. 7, which comesinto register with a small hole 48 provided in the lug 28 thatintersects the hole 44 at one side thereof, as seen in FIG. 2, so thatwhen a hollow cylindrical resilient roll pin 49, shown in FIGS. 9 and10, is compressed and pressed into place in the hole 48 it permanentlysecures the pivot pin 27 in place, since the slight amount ofcompression of the roll pin necessary for entry in the hole 48eliminates any likelihood of this retaining pin ever coming out, andthus the construction is really reduced to its lowest terms so far assimplicity and economy is concerned, as there is no need for anyriveting nor any use of a cotter pin or a lock ring. The cutout at 49'of the web of the channel at the outer end of the lever 23 enables easyaccess to the hole 48 in entering pin 49.

The corner portions 50 provided at the outer ends of the flanges 46 onthe release levers serve as positive stops to limit forward or engagingmovement of the pressure plate 20 under spring action of the levers 23and under centrifugal force of the levers in high speed operation of theengine, but, of course, the facings 21 on the clutch plate 18 normallyprevent these positive stops 50 from coming into contact with the spider26. These comer portions 50, however, do cooperate with shipping shims,like that indicated in dotted lines at 51 in FIG. 2, inserted betweeneach lever 23 and the spider 26 in the shipment of a clutch unit, thesespacers being removed after a clutch has been mounted on the flywheel.

The spider 26, as seen in FIG. 1, is of open generally triangular formand of flanged sheet metal construction providing three mounting feet 52adjacent the three release lever mountings, where bolts are entered at53 to fasten the clutch unit to the back of the flywheel. After removalof the shims 51 there remains only the adjustment of the three screws 54adjustably threaded in the extruded threaded portions 55 provided on theinner ends of the release levers. These screws, when properly adjusted,have the rounded back faces on the heads of the screws disposed in acommon plane parallel to the spider 26 and pressure plate 20, and, ofcourse, in a predetermined spaced relationship to the throwout bearing17 in the engaged position of the clutch so that it requires only apredetermined pedal movement forwardly to disengage the clutch.

In operation, looking at the construction of FIGS. 1 and 2, and theoperation diagram of FIG. 13, it is seen that I have retained themechanical advantage of the aforementioned two patents in obtainingmultiplied engaging pressure, and at the same time retained themechanical advantage derived in the disengaging operation of the levers23 by the throwout bearing 17 so that the clutch can be disengaged withlight pedal pressure, and so that with a starting pressure of only 260lbs. on the release bearing 17 (with much less pedal pressure) there is,in contrast to that, a pressure of 1,175 lbs. on the pressure plateholding the clutch engaged, not counting centrifugal effeet. The latter,by virtue of the present novel design, is of appreciable value becausethe levers 23 actually impart an appreciable amount of additionalpressure to the pressure plate due to the centrifugal effect obtained byhaving the center of gravity of each lever above the fulcrum 31, and, asseen in FIG. 1 1, the amount of this centrifugal effect can be varied byslight design changes, a substantial effect being achieved, for example,by providing a lug 54 extending rearwardly from the pivoted end of therelease lever and welding a metal weight 55 thereto by a tack weld onthe line 56. The antifriction stirrup fulcrum pivots 31 for the levers23 reduce pedal pressure in disengagement of the clutch while making thefull pressure of springs 24 available for the multiplied clutchengagement spring pressure. The stirrups 31 also compensate for anyslight changes in center distance between their V-shaped fulcrums 36 andthe pivot pins 27 during clutch operation, and it goes without sayingthat this ability to compensate for variation in center distanceaccounts in itself for an even greater reduction in friction and wearnormal in a two pin design. The present design also permits retainingthe other important advantages of:

I. the exposed pressure plate 20 for good heat dissipation and resultantlonger facing life for disk 18, and

2. locating the springs 24 between the levers 23 and the spider 26 toprotect the springs from extremely high temperatures so that the springssuffer no loss of pressure due to loss of temper.

In closing, attention is called to FIGS. 3 and 4 in which the adjustablestirrup 31 is employed with a view to retaining most of the advantagesdescribed for the construction of FIGS. 1 and 2 while permitting theadjustment of the clutch to be taken care of at the stirrups 31 insteadof at the inner ends of the levers 23' with adjusting screws 54, thelevers 23' having their inner ends 56 merely rounded for line contactdirectly with the throwout bearing 17. Levers 23 are pivoted similarlyas in the other construction by means of pivot pins 27' to the drivelugs 28' on the pressure plate 20, although in this case a lock ring 57is shown as entered in an annular groove in one end of the pivot pin toretain it, the other end having a head as shown at 58. The lugs 28, ofcourse, have sliding drive transmitting engagement on opposite sides ofthe slots 29 in the spider 26', similarly as in the other construction,but the principal difference here is the adjustable stirrups 31, each ofwhich is in the form of a T-bolt 59, the crosshead 32 on one end ofwhich provides diametrically opposed fulcrums 34' for line contactlow-friction rocking engagement with the spider 26 in the embossedportion 37' on opposite sides of the slot 36', while a separate collar60 having diametrically opposed V-shaped fulcrums 35' engaging in theindented portion 39' near the pivoted end of the lever 23' on oppositesides of the slot 38' is adjustably mounted on the shank of the T-bolt59 in front of the nut 61 that is threadedly adjustable on the threadedouter end of the shank. This permits making the adjustment of the clutchat the stirrups 31', while checking gauges for lever height are incontact with the levers 23'.

A slightly different lever construction is best shown in FIG. 4 using aseparate spring cup 62 that has a forked extension 63 that extendsthrough a hole 64 in the lever 23' and has laterally projecting V-shapedfulcrums 65 on the two arms thereof that have line contact low-frictionrocking engagement in the V-shaped cutouts 66 provided in the edgeportions of the longitudinally extending flanges 67 of the lever 23.There is also low-friction line contact diametrically of the outer endof the spring 24 on the transverse fulcrum 41' provided on the innerside of the cap 62. The inner end of the spring 24 is seated in acircular depression 40' provided in the spider 26' similarly as in theother construction. Of course, there is no reason why the cup 62 cannotbe made integral with the lever 23 similarly as the portion 42 of thelever 23 in the other construction, if that is preferred.

The operation of this adjustable fulcrum clutch construction issubstantially the same as the other clutch construction first described.

it is believed the foregoing description conveys a good understanding ofthe objects and advantages of my invention. While a preferred embodimentof the invention has been illustrated and described, this is only forthe purpose of illustration, and it is to be understood that variousmodifications in structure will occur to a person skilled in this art.

I claim:

1. In a clutch comprising a driving element and a driven element, apressure plate for holding the driving and driven elements frictionallyengaged, a lever support, a lever substantially radially disposed withrespect to and behind both the lever support and pressure platepivotally connected at its outer end to a projection on the pressureplate that extends rearwardly therefrom through an opening providedtherefor in the lever support to provide a driving connection betweenthe pressure plate and lever support, spring means caged between thelever and lever support intermediate the ends of the lever and spacedradially inwardly with respect to said pressure plate projection toapply increased clutch engaging pressure to the pressure plate in apredetermined ratio to disengaging pressure, the lever support and leverhaving registering slots provided therein between the spring means andsaid projection, and a generally ,l-shaped stirrup member insertedthrough said registering slots and having parallel cross-portions on theopposite ends thereof, one of which has low friction line contactfulcrum engagement on the lever support on opposite sides of the slottherein, the other portion having low friction line contact fulcrumengagement on the lever on opposite sides of the slot therein, saidstirrup member being oscillatable through a small angularity relative tothe first mentioned cross-portion to compensate for slight change incenter distance between the lever pivot and the fulcrum provided by thelast mentioned cross-portion of said stirrup member.

2. A clutch as set forth in claim 1, wherein the cross-portions of thefulcrum stirrup member, which are substantially parallel to one anotherand in co-planar relationship have the inner edges coined to compressthe metal to closer grain and define longer wearing fulcrum surfaces,one pair of these surfaces being on a common radius of small diameter inrelation to the curvature of the lever support surfaces which this pairis to engage, and the other pair of these surfaces being generallyV-shaped for rocking engagement with the surface on the release lever tobe engaged thereby.

3. In a clutch comprising a driving element and a driven element, apressure plate for holding the driving and driven elements frictionallyengaged, a lever support, a lever substantially radially disposed withrespect to and behind both the lever support and pressure platepivotally connected at its outer end to a projection on the pressureplate that extends rearwardly therefrom through an opening providedtherefor in the lever support to provide a driving connection betweenthe pressure plate and lever support, spring means caged between thelever and lever support intermediate the ends of the lever and spacedradially inwardly with respect to said pressure plate projection toapply clutch engaging pressure to the pressure plate in a predeterminedratio to disengaging pressure, means between the pivot and the springmeans whereby said lever is fulcrummed relative to said lever supportfor application of the pressure of said spring means to said pressureplate in a multiplied degree, the radially inner end of said lever beingmanually operable to release the clutch.

4. A clutch as set forth in claim 3, wherein the pivot pin connectingthe outer end of the lever to the pressure plate projection has anannular groove provided therein at the middle thereof, the projectionhaving a hole provided therein in transverse relationship to said pinand intersecting the annular groove provided therein, and a pin forlocking the pivot pin in place entered in said hole, the retaining pinbeing of rolled resilient sheet metal construction so as to be hollowand split lengthwise of one side and being normally of slightly largerdiameter than the hole in the projection that is to receive it, whereby,when compressed and entered in the hole, said pin is held resilientlyagainst removal from said hole.

5. In a clutch comprising a driving element and a driven element, apressure plate for holding the driving and driven elements frictionallyengaged, a lever support, a lever substantially radially disposed withrespect to and behind both the lever support and pressure platepivotally connected at its outer end to a projection on the pressureplate that extends rearwardly therefrom through an opening providedtherefor in the lever support to provide a driving connection betweenthe pressure plate and lever support, spring means caged between thelever and lever support intermediate the ends of the lever and spacedradially inwardly with respect to said pressure plate projection toapply increased clutch engaging pressure to the pressure plate in apredetermined ratio to disengaging pressure, the lever support and leverhaving registering slots provided therein between the spring means andsaid projection, a T-bolt insertable through the slots so that thecross-portion of the T is disposed transversely relative to the slot inthe lever support and rests against the lever support on opposite sidesof said slot to serve as a fulcrum for rocking engagement of the T-bolton said lever support, a collar adjustably received on the other end ofsaid bolt, which is threaded, said collar having diametrically opposedfulcrum projections engaging the lever on opposite sides of the slottherein to serve as a fulcrum therefor, and an adjusting nut threaded 0nthe end of said bolt against said collar.

6. A clutch as set forth in claim 5, wherein the fulcrum surfaces on thecross-portion of the T-bolt are rounded on a smaller radius than theradius of the surface on the lever support with which the same areadapted to engage, the fulcrum surfaces on the collar being generallyV-shaped.

7. A clutch as set forth in claim 19, wherein all of the fulcrumsurfaces are coined to compress the metal to closer grain and thusdefine longer wearing surfaces.

8. In a clutch comprising a driving element and a driven element, apressure plate for holding the driving and driven elements frictionallyengaged, a lever support, a release lever substantially radiallydisposed with respect to the lever support and pressure plate pivotallyconnected at its outer end to a projection on the pressure plate thatextends rearwardly therefrom through an opening provided therefor in thelever support to provide a driving connection between the pressure plateand lever support, spring means caged between the lever and leversupport intermediate the ends of the lever and spaced radially inwardlywith respect to said pressure plate projection to apply clutch engagingpressure to the pressure plate, the spring means comprising a coiledcompression spring, one end of which bears against the lever support andthe other end of which bears against the lever intermediate the endsthereof, the lever having a separate cup element in which the other endof said coiled compression spring is seated, the cup element having aforked extension extending through an opening provided in the leverintermediate the ends thereof, means fulcruming the two legs of the forkrelative to the lever on opposite sides of the opening therein, meansbetween the pivot and the spring means whereby said lever is fulcrumedrelative to said lever support for application of the pressure of saidspring means to said pressure plate in a multiplied degree, the radiallyinner end of said lever being manually operable to release the clutch.

9. A clutch as set forth in claim 8, wherein the separate cup has afulcrum projection on the inner side thereof diametrically with respectto the adjacent end of the spring and substantially parallel to thelever pivot and bearing against the adjacent end of the spring.

10. A clutch as set forth in claim 8, wherein the separate cup elementis an article of manufacture for engagement with the outer end of thecoiled compression spring that exerts spring pressure against the clutchrelease lever, said cup element comprising a one piece sheet metalgenerally cylindrical cup having an inwardly flanged rim portionextending toward the release lever, on diametrically opposite sides ofwhich are extensions in substantially parallel relation for extensionthrough an opening provided in the release lever, the ends of saidextensions having diametrically opposed V-shaped outward projectionsthereon for rocking fulcrum engagement with the release lever on theopposite sides thereof.

11. A clutch as set forth in claim 8, wherein the separate cup elementis an article of manufacture for engagement with the outer end of thecoiled compression spring that exerts spring pressure against the clutchrelease lever, said cup element comprising a one piece sheet metalgenerally cylindrical cup having an inwardly flanged rim portionextending toward the release lever, on diametrically opposite sides ofwhich are extensions in substantially parallel relation for extensionthrough an opening provided in the release lever, the ends of saidextensions having diametrically opposed V-shaped outward projectionsthereon for rocking fulcrum engagement with the release lever on theopposite sides thereof, the cup having an inwardly embossed transverseabutment extending diametrically thereof in parallel relationship tosaid V-shaped projections adapted to have engagement diametrically withthe outer end of said spring to space the same from the rest of the seatmember for the purpose described.

inqnan

1. In a clutch comprising a driving element and a driven element, apressure plate for holding the driving and driven elements frictionallyengaged, a lever support, a lever substantially radially disposed withrespect to and behind both the lever support and pressure platepivotally connected at its outer end to a projection on the pressureplate that extends rearwardly therefrom through an opening providedtherefor in the lever support to provide a driving connection betweenthe pressure plate and lever support, spring means caged between thelever and lever support intermediate the ends of the lever and spacedradially inwardly with respect to said pressure plate projection toapply increased clutch engaging pressure to the pressure plate in apredetermined ratio to disengaging pressure, the lever support and leverhaving registering slots provided therein between the spring means andsaid projection, and a generally I-shaped stirrup member insertedthrough said registering slots and having parallel cross-portions on theopposite ends thereof, one of which has low friction line contactfulcrum engagement on the lever support on opposite sides of the slottherein, the other portion having low friction line contact fulcrumengagement on the lever on opposite sides of the slot therein, saidstirrup member being oscillatable through a small angularity relative tothe first mentioned cross-portion to compensate for slight change incenter distance between the lever pivot and the fulcrum provided by thelast mentioned crossportion of said stirrup member.
 2. A clutch as setforth in claim 1, wherein the cross-portions of the fulcrum stirrupmember, which are substantially parallel to one another and in co-planarrelationship have the inner edges coined to compress the metal to closergrain and define longer wearing fulcrum surfaces, one pair of thesesurfaces being on a common radius of small diameter in relation to thecurvature of the lever support surfaces which this pair is to engage,and the other pair of these surfaces being generally V-shaped forrocking engagement with the surface on the release lever to be engagedthereby.
 3. In a clutch comprising a driving element and a drivenelement, a pressure plate for holding the driving and driven elementsfrictionally engaged, a lever support, a lever substantially radiallydisposed with respect to and behind both the lever support and pressureplate pivotally connected at its outer end to a projection on thepressure plate that extends rearwardly therefrom through an openingprovided therefor in the lever support to provide a driving connectionbetween the pressure plate and lever support, spring means caged betweenthe lever and lever support intermediate the ends of the lever andspaced radially inwardly with respect to said pressure plate projectionto apply clutch engaging pressure to the pressure plate in apredetermined ratio to disengaging pressure, means between the pivot andthe spring means whereby said lever is fulcrummed relative to said leversupport for application of the pressure of said spring means to saidpressure plate in a multipLied degree, the radially inner end of saidlever being manually operable to release the clutch.
 4. A clutch as setforth in claim 3, wherein the pivot pin connecting the outer end of thelever to the pressure plate projection has an annular groove providedtherein at the middle thereof, the projection having a hole providedtherein in transverse relationship to said pin and intersecting theannular groove provided therein, and a pin for locking the pivot pin inplace entered in said hole, the retaining pin being of rolled resilientsheet metal construction so as to be hollow and split lengthwise of oneside and being normally of slightly larger diameter than the hole in theprojection that is to receive it, whereby, when compressed and enteredin the hole, said pin is held resiliently against removal from saidhole.
 5. In a clutch comprising a driving element and a driven element,a pressure plate for holding the driving and driven elementsfrictionally engaged, a lever support, a lever substantially radiallydisposed with respect to and behind both the lever support and pressureplate pivotally connected at its outer end to a projection on thepressure plate that extends rearwardly therefrom through an openingprovided therefor in the lever support to provide a driving connectionbetween the pressure plate and lever support, spring means caged betweenthe lever and lever support intermediate the ends of the lever andspaced radially inwardly with respect to said pressure plate projectionto apply increased clutch engaging pressure to the pressure plate in apredetermined ratio to disengaging pressure, the lever support and leverhaving registering slots provided therein between the spring means andsaid projection, a T-bolt insertable through the slots so that thecross-portion of the T is disposed transversely relative to the slot inthe lever support and rests against the lever support on opposite sidesof said slot to serve as a fulcrum for rocking engagement of the T-bolton said lever support, a collar adjustably received on the other end ofsaid bolt, which is threaded, said collar having diametrically opposedfulcrum projections engaging the lever on opposite sides of the slottherein to serve as a fulcrum therefor, and an adjusting nut threaded onthe end of said bolt against said collar.
 6. A clutch as set forth inclaim 5, wherein the fulcrum surfaces on the cross-portion of the T-boltare rounded on a smaller radius than the radius of the surface on thelever support with which the same are adapted to engage, the fulcrumsurfaces on the collar being generally V-shaped.
 7. A clutch as setforth in claim 19, wherein all of the fulcrum surfaces are coined tocompress the metal to closer grain and thus define longer wearingsurfaces.
 8. In a clutch comprising a driving element and a drivenelement, a pressure plate for holding the driving and driven elementsfrictionally engaged, a lever support, a release lever substantiallyradially disposed with respect to the lever support and pressure platepivotally connected at its outer end to a projection on the pressureplate that extends rearwardly therefrom through an opening providedtherefor in the lever support to provide a driving connection betweenthe pressure plate and lever support, spring means caged between thelever and lever support intermediate the ends of the lever and spacedradially inwardly with respect to said pressure plate projection toapply clutch engaging pressure to the pressure plate, the spring meanscomprising a coiled compression spring, one end of which bears againstthe lever support and the other end of which bears against the leverintermediate the ends thereof, the lever having a separate cup elementin which the other end of said coiled compression spring is seated, thecup element having a forked extension extending through an openingprovided in the lever intermediate the ends thereof, means fulcrumingthe two legs of the fork relative to the leveR on opposite sides of theopening therein, means between the pivot and the spring means wherebysaid lever is fulcrumed relative to said lever support for applicationof the pressure of said spring means to said pressure plate in amultiplied degree, the radially inner end of said lever being manuallyoperable to release the clutch.
 9. A clutch as set forth in claim 8,wherein the separate cup has a fulcrum projection on the inner sidethereof diametrically with respect to the adjacent end of the spring andsubstantially parallel to the lever pivot and bearing against theadjacent end of the spring.
 10. A clutch as set forth in claim 8,wherein the separate cup element is an article of manufacture forengagement with the outer end of the coiled compression spring thatexerts spring pressure against the clutch release lever, said cupelement comprising a one piece sheet metal generally cylindrical cuphaving an inwardly flanged rim portion extending toward the releaselever, on diametrically opposite sides of which are extensions insubstantially parallel relation for extension through an openingprovided in the release lever, the ends of said extensions havingdiametrically opposed V-shaped outward projections thereon for rockingfulcrum engagement with the release lever on the opposite sides thereof.11. A clutch as set forth in claim 8, wherein the separate cup elementis an article of manufacture for engagement with the outer end of thecoiled compression spring that exerts spring pressure against the clutchrelease lever, said cup element comprising a one piece sheet metalgenerally cylindrical cup having an inwardly flanged rim portionextending toward the release lever, on diametrically opposite sides ofwhich are extensions in substantially parallel relation for extensionthrough an opening provided in the release lever, the ends of saidextensions having diametrically opposed V-shaped outward projectionsthereon for rocking fulcrum engagement with the release lever on theopposite sides thereof, the cup having an inwardly embossed transverseabutment extending diametrically thereof in parallel relationship tosaid V-shaped projections adapted to have engagement diametrically withthe outer end of said spring to space the same from the rest of the seatmember for the purpose described.